Topographical distribution of prostaglandin E receptors in human myometrium

The binding of radiolabelled prostaglandin (PG) F2 alpha and PGE2 by human myometrium was measured in vitro and the distribution and characteristics of the binding sites in non-pregnant and pregnant uteri were studied. PGF2 alpha binding sites were of low affinity (Kd 30 nM) and could be occupied by PG of the E series with higher affinity than PGF2 alpha itself. PGE binding sites were of high affinity (Kd 1.5 nM) and highly specific for PG of the E series, suggesting that they represent true PGE receptors. The concentration of PGE receptors was higher in non-pregnant than in pregnant uteri at term. In non-pregnant uteri the concentration of PGE receptors was highest in the fundus and decreased towards the cervix; in term pregnant uteri the concentration was constant in all areas. In both non-pregnant and pregnant uteri there was a significantly lower PGE binding affinity in cervix than in myometrium from the fundus-corpus area. The concentrations and affinity of PGE receptors were similar during the proliferative and secretory phases of the menstrual cycle and were not influenced by age of the patient. PGE receptors were not influenced by the presence or absence of primary dysmenorrhoea but appeared to be increased in unexplained menorrhagia.